This invention pertains to earth boring by the rotary system of drilling, and more particularly to a junk basket used near the lower end of the drill string to remove from the drilling fluid stream any heavy solids, such as broken tunsten carbide inserted teeth of roller cone drill bits, which might not easily be carried out of the well bore with the drilling fluid and which might fall back in the bottom of the hole and damage the drill bit or otherwise interfere with continued drilling.
It is already known to provide drill bits with integral junk baskets, as shown by U.S. Pat. No. 1,895,610--Del Homme. This structure has the disadvantage that the junk basket must be thrown away with the bit when the latter wears out.
It is also known to provide a basket on a special sub to be inserted in the drill string between the bit and the rest of the drill thereabove, as shown by page 3646 of the 1948 edition of the Composite Catalog of Oil Field and Pipe Line Equipment. This structure has the disadvantage of needing to be unscrewed from the rest of the drill string thereabove in order to be dumped, and since the basket is integral with the flow pipe therethrough, junk wedged therein must be dug out. In addition, the extra cost of the sub is objectionable.
A sub with a screwed-on basket is disclosed by U.S. Pat. No. 3,102,600--Jackson. To dump this basket it appears to be necessary to unscrew the sub from the pin on the lower end of the drill pipe, and the junk is then apt to fall into the box in the upper end of the sub, necessitating cleaning the box before reconnecting the sub to the pin. Alternatively, if the basket is unscrewed from the sub the junk will fall around the threads on the exterior of the sub; also, junk wedged between the basket and pipe may prevent the basket from being elevated for dumping or even from being unscrewed.* FNT *See also U.S. Pat. No. 2,894,725--Baker (ribbed sub)
Junk baskets have also been associated with other drill string equipment than drill bits, e.g. as shown in U.S. Pat. Nos.:
1,656,526--Lincoln (between drill collar and pipe) PA0 1,753,339--Hencken (down hole motor) PA0 2,376,974--Miller (down hole motor) PA0 2,670,800--Stohn (fishing tool) PA0 2,670,930--Farrar (jar) PA0 2,675,879--Middleton et al (fishing tool) PA0 2,819,038--Eckel (down hole motor) PA0 3,118,510--Kanady et al (wire line basket) PA0 3,378,089--Marsh (fishing tool) PA0 3,814,180--Oliver (fishing tool) PA0 3,856,355--Grable (down hole motor) PA0 1,518,960--Bowser (sucker rod centralizer) PA0 2,167,194--Anderson (drill stem stabilizer) PA0 2,546,295--Boice (tool joint wear collar) PA0 3,343,890--Homer (casing protector) PA0 3,978,933--Olson & McNeil (drill stem stabilizer) PA0 1,464,927--Field (drinking fountain) PA0 1,487,061--Heflin (pump cylinder protector)
but in no case is the basket readily removable for dumping. The Hencken basket is connected to the drill string and is provided with a valve controlled opening in its bottom. The Marsh basket is welded to the top sub and for dumping, it must be inverted, after the sub is disconnected from the drill string. Similarly, in none of the others of these constructions is the basket adapted for easy removal nor is it automatically freed for dumping whenever the bit is changed any more than in the aforementioned Del Homme, Reed, and Jackson constructions. The basket is either integral or screwed on or welded on.
It is known to clamp the flange of an ancillary drill stem member between the pin shoulder and box mouth of a tool joint connection, as shown in U.S. Pat. Nos.:
but in none of the foregoing is there shown a junk basket or the like which is automatically freed for dumping whenever the drill bit is disconnected.
A cuplike member with a central aperture in the bottom clamped between shoulders on other screwed together members is shown in each of U.S. Pat. Nos.:
but in neither case is junk generated below the cup the primary material to be caught, for in neither case is there a drill bit below the cup. In neither case is there provision for fluid circulation down through the interior of the cup, but sealed off therefrom, and thence back up around the outer periphery of the cup. In neither case is frequent disassembly and dumping of the cup contemplated. In neither case is the cup to be rotated during use.
It is apparent from the above discussion that the prior art has not taught a construction in which there is provided a junk basket that is readily removable for dumping and which is automatically freed for dumping whenever the drill bit is changed.